final_program_abstracts[1]

11 IMSC Session Program
Coral-based, multiproxy, multicentury, ensemble climate field
reconstructions of Pacific basin sea surface temperatures
Tuesday - Parallel Session 3
Michael N. Evans 1 and Alexey Kaplan 2
1 Dept. of Geology and Earth System Science Interdisciplinary Center, University of
Maryland, College Park, USA
2 Lamont-Doherty Earth Observatory of Columbia University, Palisades, USA
We report skill characteristics and features of an ensemble of optimal interpolation,
reduced space, climate field reconstructions (OI-CFR) of annually-averaged Pacific
Basin SST. Reduced space OI-CFR finds the target climate field estimate that is the
least-squares fit to error-weighted, calibrated proxy observations and an errorweighted,
truncated estimate of variability in the known modern target climate field.
The OI-CFR approach is modified to produce an ensemble of CFRs, assuming the
reduced space reconstruction has normal multivariate error. In this framework, the
sum of signal and error variance are constant over time, even if declining numbers of
proxy observations over time require that the ratio of signal to error variance changes
dramatically over time. The CFRs are developed from 96 annual and higherresolution
coral data series obtained from the World Data Center-A for
Paleoclimatology and PANGAEA databases, which extend with discontinuities back
to the 10th century. Similar to earlier efforts, we find two EOF patterns, possibly a
third, are reliably reconstructed: these appear to describe ENSO-related variability,
with the third pattern a homogeneous trend. Skill is improved due to better spatial
coverage and reaches 50% of target field variance in the central equatorial Pacific.
Analysis and applications of the results include (1) probability and frequency of very
strong ENSO events and decadal-timescale features over time; (2) development of
forcing functions for ensemble atmospheric GCM experiments for testing hypotheses
linking ENSO cold phase activity to drought episodes in North America over the past
several centuries.
Abstracts 129